Various polyethylenes are used throughout industry in many applications including the production of extrusion coated polyethylene laminates. Extrusion coated polyethylene laminates have many varied useful applications. One particular application for extrusion coated polyethylene laminates is in the formation of packaging articles. The extrusion coated polyethylene laminate is formed into a packaging article by bending and heat sealing extrusion coated polyethylene laminate sheets to form an enclosure. The heat seal is made by forming a molten polyethylene interface between two adjacent surfaces of the bent extrusion coated polyethylene laminate sheet followed by cooling to form a single solid polyethylene layer between two surfaces of the substrate. The resulting enclosure or container is used to package various products.
Polyethylenes used in forming these extrusion coated polyethylene laminates of medium to high density (i.e. at or above 0.925-g/cc annealed density) provide laminates and the resulting packages with very good barrier properties, low coefficients of friction, and good scuff resistance. Packages with good barrier properties retain the freshness of packaged food stuffs, while retaining moisture content. Polyethylene extrusion coated laminates with low coefficients of friction are able to be formed into packages at high processing speeds without sticking to adjacent laminates. Packages with good scuff resistance retain their good aesthetics with reduced printing ink smearing, or surface scuffing. Although these extrusion coated polyethylene laminates using a medium to high density polyethylene have desirable characteristics, they require a high temperature heat sealing process (above 95.degree. C.). When an extrusion coated polyethylene laminate is heat sealed at high temperatures, the polyethylene is oxidized or degraded to a certain extent (at higher temperatures of longer heat exposures the effect is more pronounced). The degraded or oxidized residues of the polyethylene migrate into the food stuffs contained in the packages giving rise to undesirable odors and taste for the consumer.
Low density polyethylenes (below 0,925-g/cc, more so below 0.92-g/cc) are able to be heat sealed when formed as an extrusion coated polyethylene laminate at temperatures below 95.degree. C. At these temperatures polyethylene does not have a tendency to oxidize or degrade to any significant extent. This permits the formation of packages for food stuffs that don't have undesirable tastes or odors. However, when these low density polyethylenes are formed into extrusion coated polyethylene laminates, the laminates do not have good barrier properties, low coefficients of friction, or good scuff resistance.
It would be very desirable to be able to produce extrusion coated polyethylene laminates that can be heat sealed at low temperatures, avoiding the oxidation and degradation that results in undesirable tastes and smell and be formed into packages that maintain good barrier properties, low coefficients friction, and good scuff resistance.